Multimode fiber for modulatable source

ABSTRACT

Examples include generating a signal using a modulatable source. The signal may be propagated using a multi-mode fiber to receive the signal from the modulatable source. The fiber has a diameter d and a far-field divergence angle associated with the propagated signal that corresponds to a product of the diameter (d) and the far-field divergence angle. The product may be substantially between 1 micron radian and 4 micron radian. In some examples, the propagated signal may be received at a receiver from the multi-mode fiber.

RELATED APPLICATIONS

This application is a divisional application of Divisional U.S.application Ser. No. 15/230,317 filed Aug. 5, 2016, which is adivisional of U.S. application Ser. No. 14/342,098 filed Feb. 28, 2014,which is the National Stage of International Application No.PCT/US2011/050091 filed Aug. 31, 2011.

BACKGROUND

Optical fibers may be used for communication of signals. Single-ModeFiber (SMF) may support extended propagation distances, but does notsupport multi-mode signals such as those generated by high-speedVertical Cavity Surface Emitting Lasers (VCSELs) having high modulationrates. Multimode Fiber (MMF) can support multi-mode signals, but currentMMF does not support propagation of signals over long distances at highmodulation rates due to dispersion limiting propagation effects.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

FIG. 1 is a block diagram of a multi-mode fiber system according to anexample.

FIG. 2 is a block diagram of a multi-mode fiber system including asource array, a fiber array, and optical components according to anexample.

FIG. 3 is a block diagram of an air gap connector used with a multi-modefiber according to an example.

FIG. 4 is a block diagram of a multi-mode fiber system including opticalcomponents according to an example.

FIG. 5 is a chart of optical power as a function of distance of amulti-mode fiber according to an example.

FIG. 6 is a chart of numerical aperture as a function of distance of amulti-mode fiber according to an example.

FIG. 7 is a chart of index profile difference from cladding as afunction of distance of a multi-mode fiber according to an example.

FIG. 8 is a chart of index and mode powers as a function of distance ofa multi-mode fiber according to an example.

FIG. 9 is a flow chart based on propagating a signal using a multi-modefiber according to an example.

The present examples will now be described with reference to theaccompanying drawings. In the drawings, like reference numbers mayindicate identical or functionally similar elements.

DETAILED DESCRIPTION

A multimode fiber (MMF) according to examples may be optimized forhigh-speed communication over long propagation distances. Communicationmay involve various optical sources, including lasers such as high-speedVertical Cavity Surface Emitting Lasers (VCSELs) having high modulationrates and generating signals at wavelengths such as 780 nanometers (nm),850 nm, 980 nm, 1060 nm, 1300 nm, and other wavelengths associated withsignal sources. Example fiber systems described herein may providesignal propagation distances exceeding other MMFs by more than a factorof 10. Optimized MMFs according to examples may enable low-costVCSEL-based communication at high modulation rates over long distancesand also allow for reduced complexity in optical components associatedwith propagating and/or manipulating signals, optical componentsincluding receivers, demultiplexers, splitters, connectors, lenses, andthe like.

FIG. 1 is a block diagram of a multi-mode fiber system 100 according toan example. The system 100 may include a source 102 to generate a signalto be propagated by fiber 104 and received by receiver 106.

The source 102 may be modulatable, to modulate information to betransmitted via the generated signal 108. A source diameter 112 and asource numerical aperture 114 are associated with the source 102, andmay be associated with a source d*NA, i.e., a product of the sourcediameter 112 and the source numerical aperture 114. The generated signal108 is received by the fiber 104.

Source 102 may include lasers, such as Vertical Cavity Surface EmittingLasers (VCSELs), edge emitting lasers, single-mode lasers, and othermodulatable sources. VCSELs are spatially multimode sources capable ofhigh modulation rates, and are cost effective compared to more expensivesingle-mode communication lasers that are used with Single Mode Fiber(SMF). However, VSCEL sources are not well-suited for use with SMF dueto limitations of SMF.

SMF may have a relatively small diameter, such as 5 microns (with anumerical aperture of 0.1 radians and a step index profile, forexample), according to known fiber standards such as the Internationalstandard ISO/IEC 11801 regarding general-purpose telecommunicationcabling systems (structured cabling) and/or TIA-598C standards. Thus,SMF is not ideal for use with VCSEL sources, in part due to itsinability to support the spatial multimode nature of VCSEL signals thatmay not be fully propagated by the SMF. Furthermore, SMF is associatedwith tighter alignment tolerance requirements, increasing costs andalignment difficulties for components associated with the SMF.

In contrast to SMF, MultiMode Fiber (MMF) may support multiple modesgenerated by a source. An example MMF is a Graded Index Fiber (GIF)having a 50 micron or a 62.5 micron core diameter (or greater), i.e., 50GIF or 62.5 GIF MMF. However, 50 GIF and 62.5 GIF MMFs were standardizedfor use with Light Emitting Diode sources having lower modulation rates,before the advent of VCSEL sources having high modulation rates. Thus,capabilities of 50 GIF and 62.5 GIF MMF are limited by their relativelylow bandwidth-length (BW*L) product when used with VCSEL sources. Forexample, a 50 GIF OM4 fiber (OM4 defined in TIA-492-AAAD, “Detailspecification for 850-nm laser-optimized, 50-μm core diameter/125-μmcladding diameter class Ia graded-index multimode optical fibers of OM4performance”) may have a BW*L (bandwidth-length) product of about 4.7GHz*km. Accordingly, at modulation and/or data rates of 25 Gbps, thepropagation distance is limited to less than 200 meters. At data ratesof 50 Gbps, the 50 GIF OM4 fiber would further limit propagationdistances. 62.5 GIF MMF shows further reduced propagation distancescompared to 50 GIF in view of the even larger core diameter associatedwith 62.5 GIF. Signals generated by VCSEL sources and used with 50GIF/62.5 GIF MMF are affected by dispersion and other negative effects,limiting the distance and/or bandwidth of VCSEL signals used with 50GIF/62.5 GIF MMF.

Fiber 104, in contrast to SMF and 50 GIF or 62.5 GIF MMF, may beassociated with characteristics suitable for modulatable source 102.Thus, source 102 may be based on a VCSEL source having a high modulationrate (e.g., a rate of 10 Gbps and above). Characteristics of fiber 104may include a MMF fiber having a fiber diameter 116 and a fibernumerical aperture 118. The fiber diameter 116 and fiber numericalaperture 118 provide a fiber d*NA product associated with propagatingthe generated signal 108 from the source 102 associated with a sourced*NA product, even when the signal is modulated at high rates.

The fiber d*NA product may be adjusted to allow fiber 104 to uselow-cost VCSEL sources, which are not used with SMF due the lack ofmultimode support in SMF. Fiber 104 may support high data modulationrates over extended distances, in view of the fiber d*NA product. Forexample, using the fiber 104, a VCSEL data rate of 50 Gbps may besupported over distances in excess of approximately 700 meters, incontrast to OM4 50 GIF that may be limited to a maximum distance ofapproximately 94 meters at 50 Gbps.

The fiber d*NA product associated with fiber 104 may save additionalcosts compared to SMF, because fiber 104 may allow for relaxed alignmenttolerances in fiber couplings, connectors, and other componentsassociated with the fiber 104 and/or fiber communication systemsassociated with fiber 104. Thus, components for use with fiber 104 maybe produced more economically in view of relaxed tolerances, therebymultiplying savings over an entire multi-mode fiber system.

A d*NA product (source and/or fiber) of core diameter and NumericalAperture may be a function of wavelength, and may be related to a numberof spatial modes supported by the d*NA product. At 850 nm, an exampleVCSEL may generate a signal such that the source d*NA product may be (10microns)*(0.22 radians)=2.2 micron-radian, associated with approximately4 spatial one-dimensional (1D) modes (example VCSEL sources may beassociated with source d*NA products of 2.0-2.2, and beyond). Incontrast, at 850 nm, a standard 50 GIF may have a fiber d*NA productabout 4.5 times larger at (50 microns)*(0.2 rad)=10 micron-radian,supporting approximately 18.5 modes. Thus, the 50 GIF supports spatialmodes in excess of the approximately 4 spatial modes generated by theVCSEL source.

A BW*L product supported by a graded-index fiber is approximatelyproportional to the number of 1D-modes squared, which is related to thed*NA product. Accordingly, the BW*L product can be improved using thefiber 104 supporting a d*NA product corresponding to a lower number ofmodes. Thus, fiber 104 is not associated with dispersion issues andlimited propagation distances as in the 50 GIF that supports excessivespatial modes. Thus, in contrast to the 50 GIF, fiber 104 may bedesigned as a graded index fiber having, for example, a core diameter of25 microns (25 GIF) and a numerical aperture of 0.1 radians, i.e., afiber d*NA product of 2.5 micron-radian associated with supportingapproximately 4.6 modes at 850 nanometers. The fiber 104 having a d*NAproduct of 2.5 micron-radian, associated with approximately 4 spatial 1Dmodes, may support the 2.2 micron-radian d*NA product of the VCSELsource associated with approximately 4 spatial 1D modes, while providingadditional alignment tolerances compared to SMF and increasedpropagation distances compared to 50 GIF.

Additionally, the BW*L product is proportional to a BitRate*Lengthproduct (BR*L product), which is proportional to NA as follows:

${{BR} \cdot { L \sim\frac{c}{n}}}\frac{1}{\Delta^{2}}$

where c=the speed of light, n=a refractive index of the fiber, and Δ isexpressed as follows:

${ \Delta \sim\frac{1}{2}}( \frac{NA}{n} )^{2}$

where n=the refractive index of the fiber. Thus, the BR*L product isproportional to the inverse of NA to the fourth power. Accordingly,decreasing NA by a factor of two may increase the BR*L product by afactor of greater than 10, corresponding to an increase in fiberpropagation distance.

Receiver 106 is to receive the propagated signal 110 from the fiber 104.Receiver 106 is capable of detecting the modulatable source, e.g.,compatible with the modulation rate of the modulatable source 102.Receiver 106 may include optical receivers capable of receiving thepropagated signal 110 from the fiber 104 based on the fiber diameter 116and fiber numerical aperture 118. Thus, system 100 may be used withphotonics associated with communication and/or computing devices,including optical interconnects for fiber optic communication.

Thus, a system based on example fiber 104 (e.g., VCSEL-optimizedgraded-index MMF, i.e., V-MMF) may be mode-optimized for high-speedVCSELs and may support extended bandwidth-length products. Amode-optimized V-MMF may increase in the distance that a high-speedVCSEL signal can travel along a MMF fiber. The features of examplesystems enable greater flexibility in the design of data centers orother communications applications.

FIG. 2 is a block diagram of a multi-mode fiber system 200 including asource array 201, a fiber array 204, and optical components 220according to an example. Multiple sources 202 may provide multiplegenerated signals 208 to multiple fibers 204. Generated signals 208 maybe associated with a source diameter 212 and a source numerical aperture214. Fibers 204, which may be graded-index MMFs associated with BW*Lproducts, may provide multiple propagated signals 210 to various opticalcomponents 220. Propagated signals 210 may be associated with a fiberdiameter 216 and a fiber numerical aperture 218.

Optical components 220 may include pigtail components 222, WavelengthDivision Multiplexing (WDM) link components 224, multiplexer components226, demultiplexer components 228, splitter components 230, lenscomponents 232, fiber contact connector components 234, air gapconnector components 236, additional fiber 203, and receiver 206.

The fiber 204 is well suited for various optical components 220, in partdue to supporting a lower d*NA product and corresponding number ofspatial modes. Pigtailed components 222 may be easier to design when theinput fiber 204 supports a lower number of modes, because greatertolerances may be associated with pigtail fibers of the pigtailcomponent 222. Designs of splitter components 230, such as powersplitters, mode splitters, polarization splitters, and/or wavelengthsplitters based on hollow metal waveguides (HMWGs) or zigzag approaches,may be simplified for more economical component production and relaxedalignment tolerances. The features of fiber 204 may be optimized toenable simplified and lower cost wavelength demultiplexing usingdemultiplexer components 228, WDM systems using WDM link components 224,and other optical components 220 associated with VCSEL systems such assystem 200. The fiber 204 may be associated with a beam divergenceassociated with enhanced ability to power split, collimate, and/orseparate different wavelengths of the signal, suitable for use with thevariety of optical components 220. A fiber d*NA of the fiber 204 enablesoptical components 220 to be made smaller and more economically, takingadvantage of a collimating length for a given diameter lens associatedwith fiber 204.

In an example system, a fiber 204 may be used with a wavelengthdemultiplexer component 228 to carry signals from multiple sources. Morespecifically, multiple wavelength sources 202 may be connected to awavelength multiplexer component 226 to multiplex the sources 202 into amultiplexed generated signal 208 propagated to a fiber 204. The fiber204 may propagate the signal to a wavelength demultiplexer component 228in communication with several detectors/receivers 206. Systems maysimilarly use splitters to split/combine signals.

Source array 201 may be connected to fiber array 205 based onone-dimensional (1D) or two-dimensional (2D) architectures, usingvarious connectors associated with the chosen architecture. The sourcearray 201 does not have to be the same architecture as the fiber array205. A number of sources 202 used may differ from a number of fibers 204used, e.g., by multiplexing the sources 202 and/or fibers 204. A cablemay comprise multiple fibers that are connected to multiple sources,enabling high bandwidth communication via the cable.

Example array configurations include a 2D VCSEL array of sources 202coupled into a 2D array of fibers 204. In an example, a 4×12 VCSEL arrayof sources 202 may use a different wavelength for each row. Zigzagcoupling may couple the 4×12 source array 201 into a 1×12 fiber array205 (e.g., using WDM to couple four-into-one).

Fiber connectors, such as air gap connector components 236 and fibercontact connector components 234, may be used to connect fibers 204.Fibers 204 may be optimized for use with fiber contact connectorcomponents 234 or air gap connector components 236.

Pigtail components 222 may be used, wherein a fiber is included with thepigtail component 222 for input and/or output connections. Examplefibers 204 may be used as inputs into pigtail fibers, because the fiberd*NA product associated with fiber 204 provides collimation toleranceand enables scaled-down device dimensions for facilitating manipulationof signals/light. Thus, pigtail components 222 may operate with enhancedperformance when used with fiber 204.

Additional benefits may be realized in view of the characteristicsassociated with the fiber d*NA product associated with fiber 204 as setforth above, including a VCSEL optimized multimode fiber 204 (V-MMF)that supports between 2 and 6 1D spatial modes in combination with VCSELsources, using V-MMF with VCSELs operating at data rates of 10 Gbps orlarger, using V-MMF in combination with one- or two-dimensional VCSELarrays, using V-MMF with multiple fiber array connectors (fiber contactconnectors and/or air-gap connectors using lenses), using V-MMF combinedwith WDM VCSEL links, using V-MMF with fiber pigtailed power splittingoptical buses, and other applications.

FIG. 3 is a block diagram of an air gap connector 336 used with amulti-mode fiber 304 according to an example. Air gap connector 336enables a signal to be sent through the air from fiber 304 to additionalfiber 303 using lenses 332.

Fiber 304 propagates a signal, which emerges from fiber 304 as divergingsignal 342. Lenses 332 receive the diverging signal 342, transmit thesignal as an expanded signal 340, and send the signal to additionalfiber 303 as a converging signal 344. Lenses 332 are separated by an airgap. Accordingly, two fibers may be connected without scratching orcausing the lenses 332 to contact each other. The signal beam may beexpanded, e.g., spreading out the beam from an approximately 25 microncore of the fiber to an expanded signal 340 sized at approximately 200microns at lenses 332. The expanded signal 340 is resistant to dust orother particles that would otherwise attenuate the non-expanded signal,because the portion of expanded signal 340 attenuated by a dust particleis insignificant in view of the overall signal contained by theexpansion.

A fiber (e.g., fiber 304 and/or additional fiber 303) may be terminatedwith an air gap connector due to the fiber d*NA characteristics enablingrelaxed tolerances, such that each fiber may be terminated with an airgap connector and is not limited to mating/contact connectors. An airgap connector terminating a fiber may be connected to another air gapconnector that is terminating another fiber. An array of fibers may beassociated with an array of multiple lenses.

Air gap connectors 336 are well suited to dusty environments, such asbackplane applications including a backplane of a computing system. Abackplane of a computer is dusty, and ordinary mating/contact connectorsare expensive to make and are impractical to operate successfully indirty/dusty environments. Examples of fiber 304 are compatible with airgap connectors 336, which are more economical and more robust thanmating/contact connectors in such applications.

FIG. 4 is a block diagram of a multi-mode fiber system 400 includingoptical components according to an example. Fiber 404 providespropagated signal 410 that is passed to lens 432, splitter 430, lensarray 446, and receiver 406.

Lens 432 may collimate the propagated signal 410 to be received bysplitter 430. Splitter 430 may be a zigzag optical component receiving asignal from fiber 404. Fiber 404 may be a one-dimensional input fiberarray and/or a single fiber carrying multiple wavelengths using WDM. Thesplitter 430 may be used for a WDM multiplexer/demultiplexer and/or a1×N optical power splitter. The propagated signal 410 is shown travelingfrom the fiber 404 to the receiver 406. However, the optical componentsmay be operated in reverse (e.g., multiple rows input into a singleoutput row) whereby the receiver 406 is replaced with a component toprovide multiple signals traveling toward the lens array 446 to becombined by the splitter 430 and received by the fiber 404.

The fiber d*NA product associated with fiber 404 allows for smaller andlower loss optical components, such that system 400 may have enhancedefficiency and tolerance. Splitter 430 includes selective mirrors 450and collimating mirrors 448. The selective mirrors 450 may be wavelengthselective, e.g., in the case of a WDM demultiplexer, and/or partiallyreflective, e.g., in the case of a 1×N power splitter. As illustrated,selective mirrors 450 transmit a selected range of wavelengths/power andreflect a selected range. The collimating mirrors 448 are curvedreflecting mirrors to re-collimate the beam as travels through thesplitter 430. The collimating mirrors 448 may compensate for beamdivergence, e.g., caused by diffraction. The transmitted beams arepassed to lens array 446, where the beams are focused for reception. Forexample, the beams from lens array 446 may be received by an array ofadditional fibers (not shown) or by receiver 406 (e.g., an array ofreceivers).

As a power splitter component, splitter 430 may split power to multipledifferent destinations (e.g., different fibers, lenses, receivers and/orother components). In contrast to the zigzag approach of the splitter430, a hollow metal waveguide (HMWG), which may be a pigtailedcomponent, may be used to collimate light to travel a greater distanceand have a lower number of modes. Power in the signal may dropproportionally to how much the signal is split. The number of modes ineach split of the signal may be maintained, along with the sameproportion of power of each mode in each output, to avoid mode partitionnoise.

FIG. 5 is a chart 500 of optical power as a function of distance from amulti-mode fiber according to an example. Propagated signal 510 isprovided by the multi-mode fiber, and is associated with fiber diameter516 and fiber numerical aperture 518.

As illustrated, the numerical aperture 518 is shown as a far-fielddivergence angle associated with propagated signal 510, i.e., at adistance from the fiber facet (the indicated distance measured along anaxis of the fiber). The numerical aperture 518 corresponds to NA₀ whereNA₀ is the numerical aperture at the center of the fiber where r=0.

The fiber also may be associated with modes 560 corresponding to a fiberd*NA product. Chart 500 shows the intensity pattern for the highestorder (m=4) of the modes 560 upon leaving the fiber facet of the core ofthe fiber (e.g., 25 GIF in an example). The highest order mode divergesaccording to the curve of propagated signal 510, as the modes 560propagate into free-space after leaving the fiber core. The maximumd*NA, i.e., a function of numerical aperture 518, is set by the valuefor the highest order mode of the graded-index fiber.

FIG. 6 is a chart 600 of numerical aperture as a function of distance ofa graded-index multi-mode fiber according to an example. Distances arerelative to a center of the core of the fiber. The solid inner curve,fiber numerical aperture 618 a, corresponds to a core having a radius of12.5 microns (diameter of 25 microns). The dashed outer curve, fibernumerical aperture 618 b, corresponds to a core having a radius of 25microns (diameter of 50 microns).

Numerical aperture may be expressed as a function of radius r, where rvaries from zero (at the radial center of the fiber) to a (at the outerfixed radius of the fiber core, i.e., the a is diameter of the fibercore divided by 2). For fiber numerical aperture 618 a, a=12.5 microns.For fiber numerical aperture 618 b, a=25 microns. Numerical aperture ata given radius r also may be expressed as a function of NA₀ where NA₀ isthe numerical aperture at the center of the fiber where r=0. Thus, NA(r)may be expressed as follows:

${{NA}(r)} \approx {{NA}_{o}\sqrt{1 - ( \frac{r}{a} )^{2}}}$

Numerical aperture is a quadratic value, as indicated in the expressionabove. At any radius from center of core, the numerical aperture mayassume a different value. As illustrated in FIG. 6, NA₀ corresponds to acenter of the fiber where r=0. Accordingly, NA₀ for fiber numericalaperture 618 a corresponds to 0.1 radians. NA₀ for fiber numericalaperture 618 b corresponds to 0.2 radians. The generically identifiednumerical aperture NA, in the expression for the fiber d*NA product andthe source d*NA product, corresponds to NA₀ at the center of the fiber.

FIG. 7 is a chart 700 of index profile difference from cladding as afunction of distance of a multi-mode fiber according to an example.Distances are relative to a center of the core of the fiber. The solidinner curve, fiber index 770 a, corresponds to a core having a radius of12.5 microns (diameter of 25 microns). The dashed outer curve, fiberindex 770 b, corresponds to a core having a radius of 25 microns(diameter of 50 microns).

An index profile of a fiber may be optimized for three parameters thatmay be interrelated for optimization purposes: group velocity (a measureof the relative speeds at which the modes propagated by the fiber travelrelative to each other), bending loss (losses affecting signalpropagation associated with a bend in the fiber that causes loss ofhigher order modes), and material dispersion (loss caused by dispersionof the signal within the propagation medium of the fiber). The indexprofile of the fiber may be varied to optimize the set of fibercharacteristics overall. As illustrated in the curves of FIGS. 7 and 8,the index profile may approximate a quadratic profile. The index profilemay be optimized to trade-off between material dispersion and modaldispersion, to get minimize signal degradation and maximize aBitRate*Length product (BR*L product) that is proportional to BW*L.

A fiber, such as an example V-MMF associated with fiber index 770 a, mayuse less Germanium doping in its core compared to a 50 GIF associatedwith fiber index 770 b. Less Germanium doping is used in example fibersto achieve the lower concentration peak associated with fiber index 770a, and fiber index 770 a has a lower diameter/area compared to fibersassociated with fiber index 770 b. Thus, an overall amount of doping,i.e., the amount calculated by the product of peak fiber index and fiberdiameter, is much less for fiber index 770 a. Accordingly, an exampleV-MMF associated with fiber index 770 a can be manufactured moreeconomically than a 50 GIF associated with fiber index 770 b, due torequiring less Germanium doping in the core than 50 GIF fiber.

FIG. 8 is a chart 800 of index and mode powers as a function of distanceof a multi-mode fiber according to an example. The dashed curvecorresponds to index profile values, i.e., fiber index 870 a. The solidcurves correspond to mode powers, i.e., first mode 880, second mode 882,third mode 884, and fourth mode 886.

The solid curves of first mode 880, second mode 882, third mode 884, andfourth mode 886 illustrate the shapes of the four lowestHermite-Gaussian modes that fit inside the dashed curve of the fiberindex 870 a. Each mode travels through the fiber and is limited in thetransverse dimension where that mode decays, indicated by a tail edge ofthe solid curve reaching the dashed fiber index 870 a curve. Each modeis related to a width of the dashed fiber index 870 a curve, as eachmode travels at a different effective refractive index relative to apeak index. The propagated light decays outside the core, e.g., outsidethe dashed fiber index 870 a curve where the fiber transitions into afiber cladding surrounding the fiber. Each mode (first mode 880, secondmode 882, third mode 884, and fourth mode 886) travels at a differenteffective refractive index, spaced equally in vertical steps.

The d*NA product (e.g., fiber and/or source) may be expressed as afunction of modes as follows:

${d*{NA}} = {\frac{2\lambda}{\pi} \times m_{\max}}$

where m_(max) is the maximum number of one dimensional Hermite-Gaussianmodes, and λ is wavelength.

FIG. 9 is a flow chart 900 based on propagating a signal using amulti-mode fiber according to an example. In step 910, a signal isgenerated using a modulatable source. For example, a VCSEL source isused to generate the signal. In step 920, the signal is propagated usinga multi-mode fiber. The fiber is associated with a fiber d*NA,corresponding to a product of a fiber diameter (d) and a fiber numericalaperture (NA). The fiber d*NA is substantially between 1 micron radianand 4 micron radian. In step 930, the propagated signal is received at areceiver. For example, an optical receiver may receive and decode amodulated signal from the modulatable source.

The breadth and scope of the present invention should not be limited byany of the above-described examples, but should be defined in accordancewith the following claims and their equivalents.

What is claimed is:
 1. A method, comprising: generating a communicationsignal at a source array, wherein each source of the source arraycomprises a modulatable source; propagating the communication signalusing a multi-mode fiber array to receive the communication signal fromthe modulatable sources of the source array, wherein each fiber of themulti-mode fiber array has a diameter d and a far-field divergence angleassociated with the propagated signal, corresponding to a product of thediameter (d) and the far-field divergence angle, the productsubstantially between 1 micron radian and 4 micron radian, wherein eachfiber is to extend a BW*L characteristic of the fiber, corresponding toa product of fiber bandwidth (BW) and fiber length (L); and receivingthe communication signal at an optical component via the multi-modefiber array.
 2. The method of claim 1, further comprising: receiving,from the optical component, the propagated communication signal at areceiver.
 3. The method of claim 1, wherein the multi-mode fiber arraycomprises a fiber connector to connect each fiber of the multi-modefiber array.
 4. The method of claim 2, wherein the fiber connector is anair gap connector or a fiber contact connector.
 5. The method of claim1, wherein the multi-mode fiber array is to propagate a plurality ofwavelengths based on Wavelength Division Multiplexing (WDM).
 6. Themethod of claim 1, wherein each fiber has the diameter d and thefar-field divergence angle, wherein the diameter is substantially equalto 25 microns and the far-field divergence angle is substantially equalto 0.1 radian.
 7. The method of claim 1, wherein the modulatable sourcesinclude a Vertical Cavity Surface Emitting Laser (VCSEL).
 8. The methodof claim 1, wherein each fiber is to extend the BW*L characteristic ofthe fiber based on a balance of modal dispersion, material dispersion,and bending loss associated with a refractive index profile of thefiber.
 9. The method of claim 1, wherein a number of sources of thesource array does not equal a number of fibers of the multi-mode fiberarray.
 10. The method of claim 1, wherein each fiber is a graded-IndexFiber (GIF).
 11. The method of claim 1, wherein the optical component isa pigtail component, a Wavelength Division Multiplexing (WDM) linkcomponent, a multiplexer component, a demultiplexer component, or areceiver.
 12. The method of claim 1, wherein the communication signal ispropagated at a data rate substantially equal to or greater than 10gigabits per second (Gbps) using the multi-mode fiber.
 13. A method,comprising: generating a communication signal at a source array, whereineach source of the source array comprises a modulatable source;propagating the communication signal using a multi-mode fiber array toreceive the communication signal from the modulatable sources of thesource array, wherein each fiber of the multi-mode fiber array has adiameter d and a far-field divergence angle associated with thepropagated signal, corresponding to a product of the diameter (d) andthe far-field divergence angle, the product substantially between 1micron radian and 4 micron radian; and receiving the communicationsignal at an optical component via the multi-mode fiber array, whereinthe optical component is a zigzag optical component, the method furthercomprising: splitting the communication signal using the zigzag opticalcomponent.